The law of the eternal states that if there even exists the possibility of something, then that thing exists, de facto, for in the space of infinite possibility and boundless time, the probability of any proposition reaches 1.0 in the limit and exists at once. However, like the vast field of irrational numbers, the probability of finding it may be zero. However, for those things which have value among many or otherwise encodes many shared values, its probability of existence at any moment or otherwise finding it rises.
-- MarkJanssen
Note bene: The philosophical question of "Does it exist before it is imagined?" must remain in the realm of the unknowable.
Two notes when referring to such an enigmatic metaphysical concept:
Perhaps the most significant application of this Law (and result?) is in answer to the question of the existence of God. If it is possible that there could be a perfect formulation of the Universe (akin to a unified TheoryOfEverything), then it should surely have been created, discovered, or embodied by now "somewhere".
Compare as a more specific formulation of Plato's Realm of Ideals.
See also TreeOfKnowledge